Precast concrete, L-shaped spandrels revisited: Full-scale tests

This paper presents the results from full-scale testing conducted at North Carolina State University on four precast, prestressed concrete L-shaped spandrels. The four L-shaped spandrels were each loaded through 12-ft-long (3.7 m), prestressed double tees that rested on the spandrel ledge at one end and on an independent support at the other. None of the beams were constructed with closed stirrups of mild-steel reinforcement. Rather, different arrangements of transverse L-shaped bars, welded-wire reinforcement, and longitudinal bars were provided to resist the shear and torsion induced in the spandrels. Shear and torsion forces were created by the double-tee reaction forces that were loaded eccentrically to the spandrels. The transverse and longitudinal reinforcement resisted the combined effects of vertical shear and out-of-plane bending of the web and satisfied the minimum vertical hanger reinforcement requirement for ledge-to-web attachment. All beams sustained loads well in excess of their factored design loads. Eliminating the need for closed reinforcement in slender spandrels would be of significant benefit to the precast concrete industry. This design approach would enhance the constructability of slender members, which could increase plant productivity and reduce overall costs. The paper presents the behavior of all four spandrels at various limit states, including their crack patterns and modes of failure. Researchers used these test results to better understand the fundamental mechanism developed in the L-shaped spandrels to resist shear and torsion.